Browsing by Author "Arunga, Ester E."

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    Characterization of Uromyces appendiculatus isolates collected from snap bean growing areas in Kenya
    (2012-11-02) Arunga, Ester E.; Ochuodho, J.O; Kinyua, M.G; Owuoche, J.O
    Bean rust (Uromyces appendiculatus (Pers.:Pers.) Unger var. appendiculatus) is one of the most devastating and variable pathogens of common bean (Phaseolus vulgaris L.) worldwide that can cause total crop loss. Characterization of bean rust races can help in screening resistant materials during gene pyramiding. The aims of the present research were first, to characterize bean rust isolates collected from snap bean growing areas in Kenya. Secondly, to identify which of the available rust resistance genes in common bean differentials are most effective to control rust in those areas. Snap bean leaf tissues with rust pustules were collected from different farms in eight locations in central and western Kenya during the years 2010 and 2011. Forty seven single pustule isolates were obtained and inoculated on 12 bean rust differential cultivars. For consistent results, the inoculation was repeated twice. The new international classification system and the binary nomenclature grouped the 47 single pustule isolates of U. appendiculatus into 9 different races, most of this affected the Andean gene pool. Hierarchical cluster analysis grouped the races into two major clusters depending on the virulence of the races on the host differential cultivars. The most resistant genes for pyramiding in Kenya were identified as Ur-5, Ur-11 and Ur-CNC. An important output of this study was the identification of races with potential use during gene pyramiding process.
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    Characterization of Uromyces appendiculatus isolates collected from snap bean growing areas in Kenya
    (Academic Journals, 2012-11-02) Arunga, Ester E.; Ochuodho, J.O; Kinyua, M.G.; Owuoche, J.O.
    Bean rust (Uromyces appendiculatus (Pers.:Pers.) Unger var. appendiculatus) is one of the most devastating and variable pathogens of common bean (Phaseolus vulgaris L.) worldwide that can cause total crop loss. Characterization of bean rust races can help in screening resistant materials during gene pyramiding. The aims of the present research were first, to characterize bean rust isolates collected from snap bean growing areas in Kenya. Secondly, to identify which of the available rust resistance genes in common bean differentials are most effective to control rust in those areas. Snap bean leaf tissues with rust pustules were collected from different farms in eight locations in central and western Kenya during the years 2010 and 2011. Forty seven single pustule isolates were obtained and inoculated on 12 bean rust differential cultivars. For consistent results, the inoculation was repeated twice. The new international classification system and the binary nomenclature grouped the 47 single pustule isolates of U. appendiculatus into 9 different races, most of this affected the Andean gene pool. Hierarchical cluster analysis grouped the races into two major clusters depending on the virulence of the races on the host differential cultivars. The most resistant genes for pyramiding in Kenya were identified as Ur-5, Ur-11 and Ur-CNC. An important output of this study was the identification of races with potential use during gene pyramiding process.
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    Combining Host Plant Resistance, Selective Insecticides, and Biological Control Agents for Integrated Management of Tuta absoluta
    (Hindawi, 2020-08) Nderitu, Peris W; Jonsson, Mattias; Arunga, Ester E.; Otieno, Mark; Muturi, John J.; Wafula, Geoffrey O.
    Combination of pest management strategies that minimize pesticide use and conserve natural enemies is important for a sustainable environment. Overreliance on synthetic insecticides in the management of Tuta absoluta has led to pesticide resistance leading to difficulties in managing the pest. In this regard, alternative measures need to be put in place to reduce the effects of this pest. ,e objective of this study was, therefore, to assess the effectiveness of host plant resistance, biological control, and selective insecticides when used in combination, in the management of T. absoluta in tomato production. ,e study was set up in a greenhouse in a completely randomized design involving two tomato varieties, an insecticide (chlorantraniliprole), and a biological control agent(Macrolophus pygmaeus), applied singly or in combination. Data were collected on T. absoluta damage from the lower, intermediate, and upper leaves. ,e results from this study show that a combination of insecticide with a moderately resistant variety had a significantly lower T. absoluta damage as compared with a susceptible variety combined with an insecticide. However, the moderately resistant variety when combined with insecticide showed no effect when the biological control agent was added. ,e susceptible variety significantly reduced T. absoluta damage when combined with the biological control agent. ,ese results indicate that treatment combinations in insect pest management can be utilized. ,e present study results indicate that using a moderately resistant variety (Riogrande VF) in combination with the insecticide chlorantraniliprole (Coragen®) and a susceptible variety (Pesa F1) in combination with the biological control agent (M. pygmaeus) can improve T. absoluta management. Under good habitat management, the susceptible variety will perform equally as the moderately resistant variety due to suppression of the T. absoluta populations by natural enemies. ,ese findings show the importance of environmental conservation both by enhancing natural enemy abundance and use of selective insecticide in the management of T. absoluta in tomato production. Combinations in this present study are likely to reduce insecticide doses, thereby reducing the cost of production and enhancing environmental compatibility with natural enemies.
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    Diallel analysis of Snap bean (Phaseolus vulgaris l.) varieties for important traits
    (2010-08-04) Arunga, Ester E.; Owuoche, J.O; Rheenen, Henk A. Van
    The breeding programmes of many crops use diallel analyses because of the genetic information they offer to breeders. Six morphological and agronomic traits of Snap bean (Phaseolus vulgaris L.) were studied to investigate their gene action, and to estimate the general combining abilities (GCA) and specific combining abilities (SCA) of parents and crosses. Three snap bean varieties - Amy, Monel and Morlane and two dry bean varieties - GLP 20 and GLPX 92 were used as parents in a complete diallel cross. The experiment was laid out in a randomized complete block design in a greenhouse. Significant (p < 0.01) additive and dominance effects were observed for days to flowering, plant height at flowering, number of pods per plant, pod weight per plant, pod length and pod diameter. Additive gene effects were predominant for all traits apart from pod weight. Significant (p < 0.01) maternal and non-maternal reciprocal effects were detected on plant height and days to flowering. Estimates of GCA, SCA and reciprocal effects suggested that Amy, Morlane and GLP 20 were generally the best combiners for incorporation into snap bean breeding programmes. This basic information is valuable for snap bean breeding programmes.
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    Diallel analysis of Snap bean (Phaseolus vulgaris l.) varieties for important traits
    (Academic Journals, 2010-08-04) Arunga, Ester E.; Van Rheenen, Henk A.; Owuoche, James Otieno
    The breeding programmes of many crops use diallel analyses because of the genetic information they offer to breeders. Six morphological and agronomic traits of Snap bean (Phaseolus vulgaris L.) were studied to investigate their gene action, and to estimate the general combining abilities (GCA) and specific combining abilities (SCA) of parents and crosses. Three snap bean varieties - Amy, Monel and Morlane and two dry bean varieties - GLP 20 and GLPX 92 were used as parents in a complete diallel cross. The experiment was laid out in a randomized complete block design in a greenhouse. Significant (p < 0.01) additive and dominance effects were observed for days to flowering, plant height at flowering, number of pods per plant, pod weight per plant, pod length and pod diameter. Additive gene effects were predominant for all traits apart from pod weight. Significant (p < 0.01) maternal and non-maternal reciprocal effects were detected on plant height and days to flowering. Estimates of GCA, SCA and reciprocal effects suggested that Amy, Morlane and GLP 20 were generally the best combiners for incorporation into snap bean breeding programmes. This basic information is valuable for snap bean breeding programmes.
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    Genetic Diversity of Cassava Mutants, Hybrids and Landraces Using Simple Sequence Repeat Markers
    (SCIENCEDOMAIN international, 2014-10-11) Arunga, Ester E.; Chepkoech, Emmy; Kinyua, Miriam; Kiplagat, Oliver; Kimno, Stephen
    Aims: Cassava (Manihot esculenta Crantz) is a crop with largely unexplored and unexplained potentially valuable genetic variability. The knowledge and understanding of the extent of genetic variation of cassava germplasm is important for conservation and improvement. Objective: The current study was to investigate the genetic divergence of cassava mutants, hybrids and landraces using simple sequence repeat (SSR) markers. Methodology: Genetic diversity of ten cassava genotypes was determined using 14 SSR markers. Results: Findings from this study showed that the dendrogram based on UPGMA cluster analysis revealed that SSR data indicated the existence of high divergence among the accessions. The cophenetic matrices obtained showed that SSR data marker type was r = 0.91. Conclusion: The wider genetic diversity observed using SSR markers would be valuable for efficient management of germplasm and for effective utilization of materials in breedingprogrammes to produce hybrids of desirable characteristics. The extensive genetic diversity is important to coming generations so that it copes with unpredictable environmental changes and human needs.
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    Genetic Diversity of Cassava Mutants, Hybrids and Landraces Using Simple Sequence Repeat Markers
    (SCIENCEDOMAIN international, 2014-10-11) Arunga, Ester E.; Chepkoech, Emmy; Kinyua, Miriam; Kiplagat, Oliver; Kimno, Stephen
    Aims: Cassava (Manihot esculenta Crantz) is a crop with largely unexplored and unexplained potentially valuable genetic variability. The knowledge and understanding of the extent of genetic variation of cassava germplasm is important for conservation and improvement. Objective: The current study was to investigate the genetic divergence of cassava mutants, hybrids and landraces using simple sequence repeat (SSR) markers. Methodology: Genetic diversity of ten cassava genotypes was determined using 14 SSR markers. Results: Findings from this study showed that the dendrogram based on UPGMA cluster analysis revealed that SSR data indicated the existence of high divergence among the accessions. The cophenetic matrices obtained showed that SSR data marker type was r = 0.91. Conclusion: The wider genetic diversity observed using SSR markers would be valuable for efficient management of germplasm and for effective utilization of materials in breeding programmes to produce hybrids of desirable characteristics. The extensive genetic diversity is important to coming generations so that it copes with unpredictable environmental changes and human needs.
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    A hybridization technique for orphan legumes: development of an artificial interspecific pollination protocol for Crotalaria spp.
    (Taylor and Francis, 2020-08) Wasonga, Mercy A.; Arunga, Ester E.; Neondo, Johnstone O.; Muli, Joshua K.; Kamau, Peter K.; Budambula, Nancy
    rotalaria brevidens: and C. ochroleuca commonly grown as vegetables have been extensively studied. However, information on breeding techniques is scanty. This study aimed to develop an artificial interspecific pollination protocol for two genotypes of Crotalaria with contrasting leaf and pod morphological features. The two are landraces that were previously collected from two counties in Kenya. The experimental design was a completely randomized design (CRD) in a greenhouse with C. ochroleuca as the female parent and C. brevidens as the male parent. Six-day-old flower buds of the female parent were emasculated. Pollen from a freshly opened flower was rubbed over the stigma of the emasculated flower. The pollinated stigma was inserted back into the keel petal and covered by the wing and standard petal. Data on success rate, pod, and seed production were subjected to analysis of variance. The developed artificial pollination method showed 75% success rate in the interspecies cross of C. ochroleuca and C. brevidens. Time of crossing did not significantly influence the success rate, pod, and seed production. The study demonstrated artificial interspecific pollination of Crotalaria by keel petal incision rubbing method. This protocol lays the foundation for genetic studies and improvement of Crotalaria spp.
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    Staff Profile - Dr. Esther Edith Arunga
    (University of Embu, 2015-07) Arunga, Ester E.
    Esther Arunga has a Doctor of Philosophy in Plant Breeding and Biotechnology from Moi University Kenya.
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    Tomato Leaf miner (Tuta absoluta) (Meyrick 1917) (Lepidoptera: Gelechiidae) prevalence and farmer management practices in Kirinyanga County, Kenya
    (Academic Journals, 2018-08) Nderitu, Peris Wangari; Muturi, Jamleck; Otieno, Mark; Arunga, Ester E.; Mattias, Jonsson
    Pest invasion is one of the limiting factors affecting food production. Tomato leaf miner (Tuta absoluta) (Meyrick 1917) (Lepidoptera: Gelechiidae), is an invasive insect pest of tomato. However, In Kenya, there is limited information on the level of invasion of the pest in tomato producing areas in the country. We assessed the level of invasion of T. absoluta and farmer management practices in Kirinyaga County. Tomato farmers were interviewed using questionnaires aimed at identifying the management practices used by farmers to control T. absoluta and their awareness on the insect pest. Two hundred and eight tomato farmers were interviewed, 90% of the respondents rated T. absoluta as a major pest of tomato. Results show that 94% of the respondents use synthetic chemicals in the control of T. absoluta with an average frequency of 12 times per growing season of three months with the highest frequency being 16 times. Increased use of synthetic insecticides was associated with a negative impact on the natural enemies. Among the interviewed farmers, 52 and 46% of respondents stated that after chemical spraying natural enemies disappear and are killed respectively, while 2% did not know what happened to them. It is therefore imperative to design an integrated pest management program that integrates biological control and environmentally friendly chemicals for sustainable control of T. absoluta populations.